Field of the Invention
Embodiments of the present invention generally relate to luma-based chroma intra-prediction in video coding.
Description of the Related Art
Video compression, i.e., video coding, is an essential enabler for digital video products as it enables the storage and transmission of digital video. In general, video compression techniques apply prediction, transformation, quantization, and entropy coding to sequential blocks of pixels in a video sequence to compress, i.e., encode, the video sequence. Video decompression techniques generally perform the inverse of these operations in reverse order to decompress, i.e., decode, a compressed video sequence.
The Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T WP3/16 and ISO/IEC JTC 1/SC 29/WG 11 is currently developing the next-generation video coding standard referred to as High Efficiency Video Coding (HEVC). HEVC is expected to provide around 50% improvement in coding efficiency over the current standard, H.264/AVC, as well as larger resolutions and higher frame rates. To address these requirements, HEVC utilizes larger block sizes than H.264/AVC. In HEVC, the largest coding unit (LCU) can be up to 64×64 in size, while in H.264/AVC, the macroblock size is fixed at 16×16.
Several coding efficiency enhancement tools are proposed in HEVC to reduce coding overhead. One such coding tool is luma-based chroma intra-prediction, also referred to as linear method mode (LM mode). In general, in luma-based chroma intra-prediction, chroma values in a block are predicted from down sampled reconstructed luma samples in the same block. More detailed descriptions of this coding tool for HEVC may be found, for example, in J. Kim, et al., “New Intra Chroma Prediction Using Inter-Channel Correlation,” JCTVC-B021, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, Geneva, CH, Jul. 21-28, 2010, J. Chen and V. Seregin, “Chroma Intra Prediction by Reconstructed Luma Samples,” JCTVC-C206, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, Guangzhou, Conn., Oct. 7-15, 2010, J. Chen, et al., “CE6.a: Chroma Intra Prediction by Reconstructed Luma Samples,” JCTVC-D350, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, Daegu, KR, Jan. 20-28, 2011, and J. Chen, et al., “CE6.a.4: Chroma Intra Prediction by Reconstructed Luma Samples,” JCTVC-E266, Joint Collaborative Team on Video Coding (JCT-VC) of ITU-T SG16 WP3 and ISO/IEC JTC1/SC29/WG11, Geneva, CH, Mar. 16-23, 2011.